Dynamo-electric machine



A nl 21, 1964 1.. J. REJDA 3,130,335

DYNAMIC-ELECTRIC MACHINE Filed April 17, 1961 Fl(5.l H02 ll l2 ll l2 llI2 20 I2 H 12 II II l2 l2 ll 30 20 I2 ll l2 II INVENTOR LADISLAV J.REJDA BY Jim, 131m, iwwmmm'e ATTORNEYS United States Patent 3,l3,335DYNAMQ -ELECTREQ MACH-ENE Ladislav J. Rejda, El Monte, (Iaiifi, assignorto The Epoxyiite Corporation, El Monte, Califi, a corporation ofCalifornia Filed Apr. 17, 1961, Ser. No. 103,449

9 Claims. (Cl. 310215) This invention relates to dynamo-electricmachines and more particularly to slot liners for such machines.

Certain dynamo-electric machines such as motors and generators utilizemagnetic cores in which elongated slots are disposed to receiveelectrical windings. A serious problem which confronts the art is theprevention of moisture from intruding into the windings within the slotsto cause deterioration and even short circuiting. In an attempt toexclude such moisture, it has been a practice for many years to employmoisture resistant liners in the slots surrounding the windings. Slotliners have been constructed of such materials as treated fabric orpaper, rubber, refractory materials, glass and various combinations ofsuch materials. Liners formed from these materials have been attended bypractical disadvantages. Where the liners are sutficiently flexible andworkable to facilitate manufacture and provide a compact product, theynecessarily have been so thin as to limit their moisture resistance andtheir useful life. Still further, these materials do not adequatelydissipate heat generated by the operation of the dynamo-electric device.

In recent years, thin nonmagnetic metal foil has been employed as slotliner material. The use of metal foil can be a substantial improvementover the materials mentioned above because metal even in the form ofthin flexible foil is highly impervious to moisture. Moreover, the thinfoil is very workable and easily conforms to desired configurations. Themetallic foil slot liners, however, must be carefully insulated from thewindings by g a suitable dielectric material. Moreover, a fabricationproblem is presented because the slot liner must be initially placed inthe slot and the windings emplaced within the liner with insulatingmaterial between the metallic liner and the windings. Heretofore,available devices have provided at least one opening extending axiallythe entire length of the metallic slot liner through which opening thewindings may be passed during assembly. In prior art devices, however,such openings, while permitting fabrication of the windings, haveprovided in the finished device access for the intrusion of moistureinto the windings. No satisfactory liner construction has heretoforebeen available which permits closure of the opening "ice having aslotted core of magnetic material with windings in the slots; a tube ofnonmagnetic metallic foil disposed coaxially Within each winding slot,surrounding the electrical windings which are disposed in the slot andseparating the windings from the core iron defining the slot; and asecond tube of insulating material disposed in each slot wholly withinthe metallic foil tube and surrounding the windings to electricallyinsulate the windings from the foil.

Further objects, features, and attending advantages of the inventionwill become apparent by reference to the following detailed descriptionand accompanying drawings, in which:

FIGURE 1 is a partial view in front elevation of a segment of adynamo-electric machine core, showing a first step in preparation of oneslot liner of this invention, and prior to insertion of the windings inthe slots;

FIGURE 2 is similar to FIGURE 1, and illustrates a further stage in thepreparation of the slot liner;

FIGURE 3 is a detail of one of the slots illustrated in FIGURES 1 and 2with the windings inserted in the slot;

while adequately insulating from the windings the metallic edges whichdefine the opening. I

To overcome the disadvantages of the prior art it is a primary object ofthis invention to provide an improved nonmagnetic metallic foil slotliner for the winding slots of dynamo-electric machines which liner isconstructed to provide an axially extending opening for the insertion ofthe windings through the liner during fabrication but which forms acompletely closed tube in the finished device to minimize intrusion ofmoisture into the windings and also provides complete insulation betweenthe foil and the windings.

Another object of the invention is to provide such an improved insulatednonmagnetic metal foil slot liner which is inexpensive and easilyinstalled.

Still another object of this invention is to provide an improved processfor fabricating a slotted dynamo-electric machine core with the windingscompletely enclosed in the slots by nonmagnetic metal foil slot liners,and insulated from such slot liners.

Briefly, and in accordance with one aspect of this invention, there isprovided a dynamo-electric machine FIGURE 4 is a view identical to thatof FIGURE 3 with the windings and slot liner of this invention, insection, as completed;

FIGURE 5 is a perspective view of the completed assembly illustrated inFIGURE 4; and

FIGURE 6 is a fragmentary sectional view of one of the slots showing amodified slot liner according to the invention.

With reference to FIGURE 1, there is shown generally indicated at 10 thecore of a dynamo-electric machine, usually comprised of a stack offerro-magnetic laminations. The core of which FIGURE 1 represents 21segment is annular in. configuration, having a plurality of windingslots 11 cut radially outward from the inner periphery of the annulusand extending the axial length of the core. As is well known in the art,the slots 11 receive the conductive windings of the core It).

Slots 11 may be of any desired form, but are illustrated here asfollowing the common practice to provide a narrow neck portion 12 tofacilitate closing off the slot to retain the windings therein.

The method by which the liner for a given slot 11 is prepared will nowbe described.

A sheet of nonmagnetic metallic foil 20, shown in cross-section inFIGURES 1 through 4, is placed in the core slot 11 to extend at leastthe axial length of the slot. In placing the metallic foil 20 into theslot, it is loosely folded or curled and inserted through neck portion12 until it rests against the bottom of the slot 11, as illustrated inFIGURE 1.

With reference to FIGURE 2, a thin sheet 30 of suitable insulatingdielectric material is then loosely folded or curled and, like foil 20,is inserted through neck portion 12 of slot 11 until it comes to restagainst and conforming generally with metallic foil 20. The sheet 30lies loosely within and unbonded to the foil sheet 20. Dielectricmaterial 3% should be at least as long as the sheet of metallic foil 20,but as described more fully below, is preferably longer in axial lengththan metallic foil 20.

With reference now to FIGURE 3, conductive windings 40 may be laidthrough neck portion 12 so as to lie within the slot 11 and within thefoil and insulating sheets. Where desired for the particular type ofwinding, a center stick 50 may be laid within the slot midway betweenthe first and second halves of the winding body.

Thus, it will be seen that when assembled within slot 11, the conductivewinding 40 is separated from the slot by the metallic foil 20 and thesheet of dielectric material 30.

With the reference now to FIGURE 3, foil 20 has edges 21 and 22protruding from the neck portion 12 of slot 11. Similarly, the sheet ofdielectric material 36 has opposite edges 31 and 32 protruding from neckportion 12. With reference to FlGURES 3 and 4, it will be seen thatcompletion of the slot liner is effected by first folding over theopposite edges 31 and 32 of the sheet of dielectric material 3d, therebyforming an overlapping seam extending the length of the tubular liner;similarly, opposite edges 21 and 22 of the sheet of metallic foil 20 arethen folded over in overlapping relation to form a like seam. Theoverlapping ends of the foil are bonded to each other by stronglyadherent insulating adhesive such as an epoxy resin to form a moistureproof joint. If desired the overlapping ends of the insulating liner mayalso be bonded together by an insulating adhesive.

As seen with reference to FIGURES 4 and 5, the sheet of dielectricmaterial 39 forms a closed tube, open at the ends, extending a distancegreater than the axial length of the slot, and surrounding the windings4G to insulate them from the sheet of metallic foil 29. Similarly, thesheet of metallic foil 2%) forms a closed tube, open at the ends, andextending a distance greater than the axial length of the core slot 11.The closed, moisture impermeable tube forrned by the continuous sheet ofmetallic foil 20 forms a protective barrier for the windings against anymoisture tending to travel into the slot 11. It is important to closethe inner tube of insulating material first by forming its overlappingseam and then to similarly close the outer metal tube. In this manner,the inner tube completely insulates the raw opposite edges of the metaltube, which define the opening for emplacement of the windings, from thewindings to preclude short circuiting between the windings and the metaltube.

With reference now to FIGURE 5, the sheet of metallic foil 2t) is shownextending slightly beyond each axial end of slot 11 to insure againstaxial migration of moisture reaching the windings. The tube formed bythe sheet of dielectric material 30 extends beyond each axial end of themetallic foil 2%. The purpose of the additional length of dielectricmaterial is to prevent the occurrence of an electrical short circuitbetween the windings 4t and metallic foil 20. With the overlapping seamand by virtue of the fact that the sheet of insulation, along itslength, completely surrounds the electrical conductors, it provides fullinsulation of the conductors from the metallic foil.

Illustrated in FIGURE 6 is an alternative construction according to theinvention which is identical in its structure and method of assembly tothat previously described except as detailed hereinafter. In thealternative embodiment, a sheet of nonmagnetic metallic foil Ztla isplaced in the core slot 11 to extend at least the axial length of theslot and preferably longer. A thin sheet Z-ltla of insulating dielectricmaterial is inserted through the neck portion of the slot 11 until itrests against and conforms generally to the metallic foil 20a. The sheet30a lies loosely within and unbonded to the sheet Ztla. The insulatingmaterial preferably is longer in axial length than the foil material aspreviously described. The sheets Ztla and 30a are identical to thesheets 2t) and 30 except that the former have a shorter circumference.The circumference is such that when the sheets 29a and 30a are formedinto tube shape in the slot, they leave a gap extending axially alongthe upper periphery of the tube instead of having overlapping ends suchas the sheets 249 and 3t). After the sheets Ztla and 30a are in placeconductive windings 40 are emplaced through the gap between the ends ofthe sheets in the same manner as previously described. Similarly acenter stick t may be employed if desired.

The insulating material Eltla is first closed to form a complete tube byplacing over the gap at the upper ends of the sheets a curved strip 61which is wider than the gap to form an overlap with the ends of each ofthe sheets and as long as the slot liner tube. The strip 61 may be offairly rigid paper or other insulating material. If desired the strip 61may be bonded to the ends of sheet 3% by suitable insulating adhesivematerial.

Subsequently the gap at the top of the foil sheet Ztla is closed by astrip of foil 62 which may be of the same material as the foil in thesheet Zita. The strip s2 desirably is the same length as the tube formedby the sheet Zita and is substantially wider than the gap between theends of the sheet Zita to form an overlapping seam with each of suchends. The strip 62 is bonded to the ends of the sheet Ztla by a stronglyadherent insulating adhesive such as an epoxy resin to form amoisture-proof joint.

After completion of the winding and liner assembly in either of thedescribed embodiments, some suitable means is used to close slot Illsuch as the slot wedge 60 which may be inserted as previously described.

If desired, in either of the described embodiments, the windings may beencapsulated in an insulating material within the slot liner assembly.The encapsulating medium may be introduced through the slot liner tubesthrough one end thereof or through a suitable temporary opening in theside of the tubes which opening is later closed and sealed. Sufficientencapsulating medium may be introduced into the tubes to fill theinterstices of the windings and the spaces between the windings and theslot liner. Any suitable insulating encapsulating medium may be employedas described in my co-pending application Serial No. 86,254 filedlanuary 31, 1961, entitled Encapsulation of Electrical Power Component.A preferred encapsulating medium is epoxy resin as set forth in the saidco-pending application. If desired, the epoxy resin encapsulating mediummay be used to seal the overlapping seams of the paper and foil slotliners of either embodiment. Alternatively the seams may be presealedand the encapsulating medium subsequently introduced.

Preferably, the axial ends of the slot liner tubes are secured andcovered by an insulating material such as epoxy resin. The sealingmaterial may be sprayed or otherwise applied on the ends of the tubes.Such end closure desirably is accomplished whether or not the windingswithin the slot liner assembly are encapsulated.

Accordingly, the slot liner tube is completely closed so as to bemoisture-proof and gas-proof.

The dielectric material for the sheets St) or 39a may be any suitableinsulating material including without limitation paper. Mylar, varnishedfabric, glass, mica, polyester resin, or combinations of any of theforegoing. T1 e foil of sheets 20 or Ztla may be formed of any suitablenonmagnetic metal such as stainless steel or aluminum. Stainless steelis preferred because of its greater strength. The foil sheets should becontinuous and unbroken to insure moisture impermeability. Epoxy resinswhich may be employed are set forth in application Serial No. 675,- 280filed July 31, 1957, entitled Epoxy Carboxylic Acid DianhyclrideCompositions.

In view of the foregoing disclosure, it will be seen that the slot linerof this invention is inexpensive, simple and reliable. The metallic foilis ideal for its strength, flexibility and moisture impermeability.Since it completely surrounds the winding, it is difficult or impossiblefor moisture entering the slot from the lamination at any point to reachthe windings without first traveling at least to the end of the metallicfoil in either direction. It is equally usable with or withoutadditional treatment of the unit, such as encapsulating the winding inan insulating material; it is easily adaptable to manufacturingprocesses, either manual or mechanical and requires no extensivepreliminary preparation or additional parts other than those commonlyavailable.

While the invention has been illustrated and described with respect to aspecific embodiment, it will be apparent to those skilled in the artthat various modifications may be made without departing from the scopeof the invention as defined solely by the claims.

I claim:

1. An insulating liner for an electric motor core winding slot, saidliner comprising a nonmagnetic metallic foil tube disposed within andcoaxial with said slot, said tube being formed by a sheet of foil withthe longitudinal edges engaging each other to form said tube, bondingmeans sealing together the entire length of said engaging edges toprovide a substantially moisture-proof wall which completely surroundsthe motor winding in the slot, and means between said tube and saidwinding electrically insulating said windings from said metallic foil.

2. An insulating liner for an electric motor core winding slot, saidliner comprising a substantially moistureproof tube coaxially withinsaid slot and extending at least the length of said slot and surroundingthe winding conductors in the slot, said tube being formed by a sheet ofnonmagnetic metallic foil having opposite edges thereof overlapped,bonding means forming said overlapped edges into a substantiallymoisture-proof searn generally parallel to the-slot axis, and meansbetween said tube and said winding electrically insulating said windingconductors from said metallic foil.

3. An insulating liner for an electric motor core winding slot, saidliner comprising a substantially moisture-proof tube coaxially withinsaid slot and extending at least the length of said slot and surroundingthe winding conductors in the slot, said tube being formed by a sheet ofnonmagnetic metallic foil having opposite edges thereof spaced apart andcovered by a strip of nonmagnetic metallic foil overlapping and bondedto said edges to form a substantially moisture-proof seam generallyparallel to the slot axis, and means between said tube and said windingelectrically insulating said winding conductors from said metallic foil.

4. An insulating liner for an electric motor core winding slot, saidliner comprising a first substantially moistureproof tube of nonmagneticmetallic foil coaxially within said slot and extending at least thelength of said slot, a second tube of insulating material disposedwithin said first tube and surrounding the winding conductors withinsaid slot, each of said tubes comprising a bent sheet having overlappingopposite edges bonded to each other to form a substantiallymoisture-proof seam generally parallel to the tube axis, said secondtube having both of its overlapping edges inside the inner wall of saidfirst tube.

5. The structure as recited in claim 4 wherein said second tube extendsbeyond said first tube at each axial end thereof.

6. The structure as recited in claim 4 wherein said second tube ispaper.

7. An insulating liner for an electric motor core winding slot, saidliner comprising a first substantially moistureproof tube of nonmagneticmetallic foil coaxially within said slot and extending at least thelength of said slot, at second tube of insulating material disposedwithin said first tube and surrounding the winding conductors withinsaid slot, each of said tubes comprising a bent sheet having spacedopposite edges covered by a strip overlapping and bonded to said edgesto form a seam generally parallel to the tube axis, said second tubehaving both of its overlapping edges inside the inner wall of said firsttube.

8. A dynamo-electric device comprising a core of magnetic materialhaving a plurality of slots, a current carrying winding in each of saidslots, a tubular liner coaxially within each of said slots extending atleast the length of the slot and surrounding the winding in the slot,said liner comprising a substantially moisture impermeable outer sheetof nonmagnetic metallic foil and an inner sheet of insulating material,each of said sheets being bent into the tubular configuration of saidliner and having an overlapped seam extending the length of said linerat the top of the slot, bonding means forming the overlapped seam insaid outer sheet into a substantially moisture-proof joint along itsentire length, said inner sheet having its overlapping seam inside theinner wall of said outer sheet.

9. An apparatus as recited in claim 8 wherein said inner sheet extendsbeyond the length of said outer sheet at each end thereof.

References Cited in the file of this patent UNITED STATES PATENTS2,495,010 Kirkpatrick Jan. 17, 1950 FOREIGN PATENTS 1,243,701 FranceSept. 5, 1960

1. AN INSULATING LINER FOR AN ELECTRIC MOTOR CORE WINDING SLOT, SAIDLINER COMPRISING A NONMAGNETIC METALLIC FOIL TUBE DISPOSED WITHIN ANDCOAXIAL WITH SAID SLOT, SAID TUBE BEING FORMED BY A SHEET OF FOIL WITHTHE LONGITUDINAL EDGES ENGAGING EACH OTHER TO FORM SAID TUBE, BONDINGMEANS SEALING TOGETHER THE ENTIRE LENGTH OF SAID ENGAGING EDGES TOPROVIDE A SUBSTANTIALLY MOISTURE-PROOF WALL WHICH COMPLETELY SURROUNDSTHE MOTOT WINDING IN THE SLOT, AND MEANS BETWEEN SAID TUBE AND SAIDWINDING ELECTRICALLY INSULATING SAID WINDINGS FROM SAIL METALLIC FOIL.